Add a 2D efficiency class to the TrigInDetAnalysis

Adds a 2D efficiency class for extended functionality.

This is a copy and extension of an existing class to add support also for 2D histograms. Sadly, cannot easily form this from a template from the 1D version because of the horrible root TH1 and TH2 classes. Perhaps will make additional changes to template to avoid code duplication in the future.